4 Answers
4

As explained in this answer, a UIButton or other UIControl that is a subview of a scroll view will automatically respond to taps while letting the scroll view handle drags. However, buttons that are subviews of the scroll view will also move with the scrolled content, rather than remaining in the same position on the screen as the content scrolls beneath them. I assume this is why you don't want to put the buttons into the scroll view.

If that's the case, you can get the desired behavior with one more step. Put all your buttons into a UIView that is a subview of the scroll view, then in the scrollViewDidScroll method of the scroll view's delegate, set that view's frame.origin to the scroll view's contentOffset. I just implemented this in my app and it's working great, without having to do any subclassing or get involved with the responder chain or touch events.

Add a transparent, custom UIView as big as the entire scroll view contentSize to the scroll view, over all the other views. (Or alternatively, make it as big as the scroll view width/height and simply move it every time the scroll view moves.) When the scroll view decides to pass on its touches to its subviews instead of dragging, this will be the first thing hitTested.

Override the hitTest method for the UIView. Check if the touch is within your button frame. If it is, return the button; if not, return nil.

In effect, you'd be tricking the scroll view into thinking that the button is one of its subviews. I'm not certain this will work as I haven't actually tried it, but it seems entirely sensible.

I tried this, but couldn't make it work. The problem is that hitTest is called on the view whether you swipe the scroll view or just tap it, so the custom hitTest method doesn't know whether to pass the event through to the scroll view, or redirect it to the button. I also tried using touchesMoved in the custom view to calculate whether it's receiving a touch or a tap, but by the time touchesMove is called, the hitTest method is finished, so there's no way to respond conditionally there.
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arlomediaJul 27 '11 at 21:37

Try adding a UIPanGestureRecognizer to the UIBUtton. In the callback you specify to handle the pan (drag), you need not implement anything. Then, set cancelsTouchesInView to YES. This will cause your button to passed drag gestures to the other views.

I ran into a similar situation where I had a UIScrollView with two UIView subviews. Each UIView contained a UISlider. I wanted to catch (and drop) vertical drags (which is where the gesture recognizer came in), but I also needed horizontal scrolls to work in the slider as you'd expect AND to pan the scroll view left and right. This was the solution. (The gesture recognizer was attached to each UIView.)